


Insomnia

by SprucePines



Category: Gravity Falls
Genre: F/M, Incest, Masturbation, Pseudo-Incest, Sibling Incest, Twincest
Language: English
Status: Completed
Published: 2015-02-12
Updated: 2015-02-12
Packaged: 2018-03-11 23:09:51
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,200
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/3336248
Author URL: https://archiveofourown.org/users/SprucePines/pseuds/SprucePines
Summary: <blockquote class="userstuff">
              <p>After accidentally bumping into each other after Mabel had showered, both Dipper's and Mabel's imaginations give them strange thoughts. In their respective beds that night, neither can sleep. They each decide to rub one out, hoping that will cure them of their preoccupation. Their minds, though, have other ideas.</p>
            </blockquote>





	Insomnia

**Author's Note:**

> This story alternates between both Dipper's and Mabel's perspective. To differentiate, I adopted the following style: Sections from Dipper's perspective are in bold, Mabel's perspective in italics, and both together...I think you can find that out for yourself. Also, due to the use of italics, their internal thoughts are surrounded by asterisks.

**Fuck fuck fuck fuck fuck...**

**Dipper looked over at his alarm clock. 12:30 am. It was like it was mocking him. *What's wrong, Dipper? Can't sleep?***

**If looks could kill, Dipper would have melted that damn alarm clock long before now. Of course, if he were in the Dreamscape, he could do just that. But if he were in the Dreamscape, he'd be asleep and he wouldn't need to be pissed at his alarm clock...**

**He looked past the clock to the far wall. On the other side of that wall lay the reason he couldn't sleep. Well, that and his own fucked up head.**

**His twin sister, Mabel.**

_Shit shit shit shit shit..._

_Mabel glared at her alarm clock for the twenty-seventh time that night. 12:30 am, it read. Not even two minutes since the last time she checked._

_She groaned. Why would sleep not come?_

_She knew the reason. She looked beyond her clock to the wall. Past her Boyz Crazy posters lay the reason she couldn't sleep. That and her own twisted mind._

_Her twin brother, Dipper._

**Despite himself, his mind decided to replay that day's events, starting with that morning. How he had come out of this bedroom clad in only his boxers to go shower. As he neared the bathroom door, it opened and out stepped Mabel, wrapped in a towel. He came to a halt and they both stood there for a moment, and their eyes locked.**

**All at once, it occurred to him how pretty she was. Well, he always knew it to be true, mostly because Mabel liked to remind him of that fact any chance she got. But there was something about the way the light from the bathroom hit her skin that made her seem to really shine.**

**Against his better judgment, his eyes wandered down her face to her bare shoulder. She had always taken great care of her skin. He couldn't recall ever seeing so much as the tiniest pimple on it, even with their adventures in Gravity Falls. From her shoulder, it was just a short journey to her upper chest. Though covered by a layer of thick, soft cotton, it was obvious that she was becoming a truly lovely young lady and...**

**Dipper's eyes widened as he felt the stirring in his shorts.**

***No. Nononononono! Dipper Pines, you are not going to get turned on by your own sister!***

**He quickly stepped past Mabel and into the bathroom. She just as quickly walked past him towards her room. Most likely surprised at being seen wearing so little. He closed and locked the door, then leaned back against it. *What the hell, Dipper, get a hold of yourself. Well, at least you didn't...***

**His thought trailed off as he looked down, where he saw himself sporting a visible tent in his boxers.**

***Fuck!***

_Against her wishes, her brain thought it would be great fun to show her the events of the day, starting from after her shower. She had just come out of the bathroom to find her brother standing in the hall, wearing nothing but his boxers. Their eyes met._

_*Ah...my bro-bro* she thought. He'd certainly changed since that summer in Gravity Falls. In a good way, of course! He'd been letting his stubble grow out a little, and she had to admit it looked good on him. She kinda wanted to feel it and see how its texture compared to the hair on top of his head._

_Her eyes trailed down to his bare torso. Between his training with the manotaurs and being worked ragged by Grunkle Stan around the Mystery Shack, Dipper had really toughened up. For being a science and math nerd he looked pretty darn buff, if she did say so herself._

_Allowing her eyes to continue wandering she caught sight of more hair, this time on his stomach. *Now what was it they call that? A happy trail! That's it! Yeah, a happy little trail of hair leading all the way...down...to..._

_That was when she noticed that Dipper shorts looked a little tented. And just after that was when she realized that for the last several seconds, she'd had butterflies in her stomach. But she only felt that when she..._

_*Whoa whoa whoa, stop the presses! Mabel Pines, you cannot have the hots for own brother!*_

_She cast her eyes sideways and made her way past Dipper and into her bedroom as fast as she could but as inconspicuously as possible. Dipper strode past her and quickly closed and locked the bathroom door. Probably shocked at being seen almost naked. Closing her door, she lightly banged her forehead against it. *What the hey hey, Mabel, where did that even come from? There's no way that you could possibly...*_

_The tingling sensation she was feeling begged to differ._

_*Oh...poopie...*_

**He had spent the entirety of the day trying to avoid Mabel whenever possible. There were a few times when it simply couldn't be helped, such as the ride to and from school in Dipper's car and the classes they shared. He'd considered asking Mabel if she wanted to call a friend for a ride, but determined that might make her question him, and he didn't want to risk bringing up that morning. At least until he got his head cleared. Thankfully, Mabel wasn't as talkative as she usually was. At lunch, he was quick to seek out his friends and sit with them, but Mabel didn't seem perturbed. In fact, she seemed quite satisfied eating lunch with her own friends that day.**

**Supper that evening, however, destroyed any progress he had made during the day. First of all, it was bad enough having no choice but to sit across from his sister (*your sister!*, he kept reminding himself), but to compound it by adding their parents into the mix? All through, he kept himself focused on his meal, letting his parents have all the conversation. He only spoke when spoken to, keeping his answers concise.**

**He might have made it completely, but when he reached for a second dinner roll, his fingers found themselves intertwined with Mabel's. He stared at their hands, dumbly, for a moment, and before he could stop himself his eyes followed her arm up, up, up until he was looking into her face.**

**Her eyes were staring directly into his.**

**All at once, he imagined the silky smooth skin of her bare shoulder, just above a pair of developing breasts and wouldn't you really like to see what they look...*NO!***

**He pulled his hand back as if he had touched molten magma. He stood (perhaps a bit more panicked than he would have liked) and asked if he could be excused from the table, saying he had some homework to start on. He deposited his dishes in the kitchen sink and made his way to his bedroom. As soon as he closed the door he sank to the floor, his fists pressed against his temples. A moment later, he heard the click of Mabel's door closing.**

**He sighed and cursed himself.**

_She'd spent the rest of the day trying to stay as far away from Dipper as she could. It wasn't easy; there were times when it just couldn't be helped. She briefly thought about finding another way to school, but decided that might make Dipper suspicious, and she did not want to spark a conversation with him right now. Not until she got herself under control. So she settled for just staring out of the window. Luckily, Dipper kept his attention on the road (well, apart from singing along with his BABBA CD). When lunchtime came, she found her friends and sat with them. Dipper didn't seem to mind, though. In fact, he went and sat with his own friends without a word._

_Supper proved disastrous, though. She knew there was no avoiding sitting across from Dipper (*he's your brother!* she kept telling herself), but having their parents there, too, just upped her stress factor. She let her parents drive the conversation, keeping her answers short and simple and just focused on eating._

_She almost succeeded, but she had to decide she wanted a second dinner roll. As she reached toward the basket, she found her fingers threading between Dipper's. Before she knew what was happening, her eyes were making their way up his flannel shirt sleeve and into his face._

_His eyes were staring directly into hers._

_Instantly, the image of Dipper in his boxers came bounding into her mind's eye, that trail of hair running from his stomach down into his shorts and would you look at that bulge, wouldn't you like to see what he's got...*STOP!*_

_She withdrew her hand as if she'd touched boiling water. Dipper had stood and asked to be excused. Just after he'd left, she stood and asked to be excused herself. After she put her dishes in the sink, she walked to her room. She saw that Dipper had closed his door. She did the same with her door, flopping herself on her bed and staring at the ceiling._

_She closed her eyes and scolded herself._

**And now here he was, wishing desperately that he could just purge his mind of the entire day and go to sleep.**

**From down below, he once again felt himself stirring.**

**He growled softly. *Fine,* he thought, *if that's what you want so bad, we'll rub out a quick one. Then will you let me go to sleep?***

**He lowered his boxers, revealing his growing erection. He sighed and thought back to their first summer in Gravity Falls, recalling the image of Wendy in her swimsuit at the pool. They'd long since settled on just being friends, but what she didn't know wouldn't hurt him, right? With a small grin, he took himself in hand and slowly began stroking.**

_And so she lay, wanting her mind to just be drained of that day's events and wishing sleep would just take her away._

_But that fluttery feeling down below just wouldn't go away._

_She sighed. *Alright,*she said to herself, *if I do this, will you let me go sleep?*_

_She lifted the hem of her nightshirt. She took a deep breath and thought back to that first summer in Gravity Falls and when she first met Mermando. It was never meant to be, but that shouldn't stop a girl from taking care of her business, right? The corners of her lips curled up as she slid her fingers into her panties and slowly began rubbing._

**In his fantasy, Dipper was meeting Wendy for a midnight swim at the pool. They weren't really swimming of course, just treading water around each other and splashing each other. Wendy's the one who breaks the ice, reaching out and gently grasping Dipper's crotch. In his bed, Dipper moans softly as he imagines the real Wendy doing the same. "Whoa, what'cha got there, Dipper?" Dream-Wendy asks. "If I didn't know any better, I'd think you wanted to ditch the swimsuits."**

**"Maybe I do," Dream-Dipper replies. Dream-Wendy laughs like he's kidding, but reaches for the straps of her suit. She pulls them down over her shoulders. His mind's eye moves from her now bare shoulders up to her face.**

**But instead of Wendy, it's now Mabel standing in the pool, her towel wrapped around her torso. "Do you want to see them, bro-seph? All you have to do is ask." And then she begins to peel away the layer of cotton...**

**Dipper's eyes snap open and he gasps. *Can't you even let me have this?!* He closes his eyes and tries again, trying his best to ignore how much precum his erection produced when Mabel appeared.**

_In her fantasy, she's snuck off from the Shack to see Mermando at the pool in the middle of the night. Being a merman trapped in a municipal pool, he's happy for the company. She floats along atop an inflatable while Mermando entertains her with flips. After a particularly large splash, Mermando surfaces and drifts up to Mabel. "Ah, my sweet Mabel," Dream-Mermando said, "I wish that this night, she would never end."_

_"Mmm, Mermando, I wish this night would never end, too," Dream-Mabel purrs. She reaches out and places her hand against Dream-Mermando's cheek and slowly runs it down his smooth chest. As her hand continues along Dream-Mermando's chest, it gradually becomes a bit firmer and--is that hair? Why is there hair? She looks down to see that Mermando's fish tail had changed to a pair of human legs. Looking back up, Mermando has become a boxer-clad Dipper, and her hand is drifting to the forbidden zone._

_"It's okay, Mabel," Dream-Dipper says. "You know you want to." He gently takes her hand and guides it down to the waistband of his boxers..._

_Her eyes spring open. *Oh, come on!* She closes her eyes and works to come up with a new fantasy, choosing not to acknowledge how wet she'd gotten when Mermando became her brother._

**Now he's back in the underground bunker, along with Wendy, Mabel and Soos. Mabel is about to shove Dipper into the decontamination chamber, but even though he knows it's coming, he doesn't mind. He plays the part the way Mabel expects, and when the door slams shut he knows that now is his chance. He stands up and is face to face with Wendy.**

**"Ugh, where are the lights?" Dream-Wendy asks, reaching for the lone pull cord in the room. They are showered by decontaminant, soaking them through before jets of air blow them into each other. Dipper's head find itself sandwiched between Wendy's breasts, but instead of his original reaction he now takes the time to enjoy the feeling. He brings a hand up and grasps one of them, eliciting a high-pitched moan. High-pitched? Wendy's voice isn't that high. He pulls himself away and looks to find that Dream-Wendy's green flannel shirt has been replaced with a white cotton bath towel.**

**"Dipper?" came a familiar voice, but the wrong familiar voice. He looks, and sure enough, Wendy has once again been replaced by his sister. Her face is expectant. "That's not all there is, Dipper," she coos, pulling his hand away from her breast and leading it down, down, down...**

**He sits bolt upright in bed, his fantasy again broken.**

_She's in the attic of the Mystery Shack, surrounded by the members of Sev'ral Timez. Sure, they were genetically engineered, but they still had the equipment and besides, this whole situation is getting ridiculous! They were performing "Mabel Girl," turning it into a strip tease. Dream-Mabel is eating it all up, basking in the perfect boy bods around her._

_As they gyrate and peel off their clothing, Deep Chris takes his hat and tosses it across the room like a Frisbee. Dream-Mabel laughs as it lands on her face and lands in her lap. She looks at it...only now it's become Dipper's ball cap. She looks up and the boy band has been replaced by five Dippers, all in various states of undress and all looking at her with lust in their eyes. The Dream-Dipper nearest to her smirks as he begins to lower his shorts..._

_She snapped back to reality and groaned._

**He was starting to get desperate. He closed his eyes and conjured up another image of Wendy, this time in a fancy dress. They're twirling on the dance floor, the center of attention. The moment is perfect. He leans in for a kiss...but Wendy's face morphs before his eyes to become Mabel, her lips lush and inviting...**

_This was beginning to make her mad. She shut her eyes again, bringing back Norman of all people. Okay, he'd really been a group of gnomes in disguise, but this is her fantasy and this time he's going to be a vampire, dammit! They're holding hands as they walk through the graveyard. He brings them to a stop and takes both her hands. He brings their faces closer, she puckers her lips...but his face transforms into Dipper's, the gap still closing..._

**Frantically, he pulls every girl he'd ever known, even Pacifica, but they all melted back into his sister, and their lips are about to meet...**

_In desperation, she tried every boy she'd ever met, even Gabe, but they all turned back into her brother, their faces getting closer and closer..._

**As their lips come together, his erection throbs and he moans. He is lost now.**

_As they kiss, she purrs and her opening begs for more. She can't hold back._

**_The kiss deepens. His hands wrap themselves around her waist, her hands tangle themselves in his hair._ **

**_He parts his lips slightly and extends his tongue. She welcomes it into her mouth and their tongues dance._ **

**In his bed, he groans audibly and pumps harder.** _In her bed, she moans and inserts two fingers into herself, her hips bucking._

**_They quickly lose their clothes. He brings a hand up and gently caresses her breast. She lowers a hand and grasps his buttocks, grinding themselves together._ **

**_They lower themselves to the ground, both of them ravenous. He begins kneading her breasts, leaning in and taking a nipple into his mouth. She drags her fingernails down his back._ **

**_In their beds, they're both panting. Nothing's ever been so intense before._ **

**_Unable to wait anymore, she reaches down and takes his member in her hand. Its heat radiates into her hand as she guides it into her. Her warmth spreads into him as he penetrates her._ **

**_Simultaneously, they moan._ **

**_He slowly starts to move, but neither of them can hold back and soon they're both moving. They both have a desperate need, and they've gone too far now._ **

**In his bed, his hand moves faster.**

_In her bed, her free hand reaches up and begins massaging her breast._

**_He thrusts into her as she moves her hips in time. They're both so close. Their lips meet again._ **

**Before he can stop himself he moans, "Mabel..."**

_"Dipper..." she moans, unable to hold her tongue._

**_Together they cum, spasming uncontrollably._ **

**As he came down from the high, he looked down at himself. His chest was covered and more was oozing from the head of his penis.**

_As she recovered she brought her hand up to see. It was practically drenched and her panties felt as though they were glued to her._

**A knot began to form in his throat as he realized just what he had done. His lip began to quiver as he reached for a wad of Kleenex to clean himself.**

_Her chest tightened as what she'd done finally occurred to her. She fought back tears as she stood to change her panties._

**As he threw the last of the tissues away, he lay back down and closed his eyes. Thankfully, he could feel himself finally drifting off.**

_As she laid back down on her bed, she could feel sleep finally come to claim her for the night._

**_Just before they each fell asleep, they both had the same thought._ **

**_*It's never been like that before.*_ **


End file.
